1. Field of the Invention
The present invention relates to a magnetic resonance imaging method and apparatus, and more particularly, to a magnetic resonance imaging method and apparatus suitable for imaging of a fluid portion in the body such as blood flow and cerebrospinal fluid (CSF).
2. Description of the Prior Art
A method of imaging the fluid portion in the magnetic resonance imaging is discussed in detail in an article of IEEE TRANSACTION ON MEDICAL IMAGING, VOL. MI-5, NO. 2, SEPTEMBER 1986, PP 140-151. The imaging principle of the blood flowing portion is to utilize a pulse named a flow encode pulse and generating a phase shift by movement. In other words, when the flow encode pulse exists in a flowing direction, the phase shift occurs in accordance with a velocity. Subtraction between images is performed between the phase-sensitive pulse sequence including the flow-encode pulse and the phase-insensitive pulse sequence not including the flow encode pulse. Since blood flow in blood vessels is laminated, different phase shift occurs in accordance with a distance from a center of the blood vessel when imaging is made by the phase-sensitive pulse sequence. Consequently, projection data is canceled each other and no signal is generated from the blood vessels. On the other hand, in the phase-sensitive pulse sequence, since the phase is not shifted due to movement, a signal is generated from the blood vessels even in the laminated blood flow. In a stationary portion, a signal is generated in any pulse sequence, while when subtraction is made between the two pulse sequences, the signal of the stationary portion disappears, so that an image of only the blood vessels appears. This method is named the subtraction method.
According to such a technique, however, a signal is missing in a portion in which phase compensation in the phase-insensitive pulse sequence is not sufficient, for example, such as a portion in which a turbulent flow occurs or a portion in which an acceleration is provided, and it is difficult to judge whether the missing of the signal is caused by a disease or a trouble in measurement.